Reducing zinciferous materials containing lead



Patented 4, 1930 UNITED STATES PATENT. OFFICE EARL E. BUNCE AND GEORGE'1. MAHLER, OF PALMERTON, PENNSYLVANIA, ASSIGN- 035 TO THE NEW JERSEYZINC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEYApplication filed January 4, 1928. Serial No. 244,519.

This invention relates to the reduction or smelting of zinciferousmaterials containing leadand has for its object the provision of certainimprovements in the smelting of such zinciferous materials whereby aneffective elimination of lead is obtained.

ticularly applicable to the pyrometallurgical treatment of such zincconcentrates and other zinciferous materials containing lead, since bythe practice of the invention high grade zinc products substantiallyfree from lead can be produced therefrom.

The gaseous product resulting from the smelting of a charge ofzinciferous material containing lead consists for the most part ofmetallic zinc vapor, carbon monoxide, and a small amount of lead. In theheretofore customary zinc smelting practices, any lead in the gaseousproduct will,'for the most part, accompany the zinc'vapor and therebycontaminates the final zinc product. Throughout this specification andthe appended claims, we have used the Word lead in a general sense andmean to embrace thereby not only metallic lead but compounds of lead. Onthe other hand, such lead-content figures as are given in thespecification are percent-v ages of lead calculated as metallic lead.

In addition to lead, the zinc smelting charge may and usually doescontain one or more other contaminating metals which, like lead, boil attemperatures above the boiling temperature of zinc but which find theirway into the gaseous product of the zinc smelting operation and therebycontaminate the zinc product obtained therefrom. While these othercontaminating metals, such, for examleadin ple as tin, antimony,bismuth, aluminum,

magn ordinarily present in relatively small percentages, frequentlyamounting to mere traces, they very often deleteriously influence theproperties of the ultimate zinc product.

The ob ect of our present invention is to provlde a pyrometallurgicaltreatment for zinciferous materials containing one or more of theaforementioned contaminating metals 1n the course of which a substantialremoval of the contaminating metals is effected, thereby making possiblethe recovery of a purer and more desirable zinc product than can beobtained by the heretofore customary methods of zinc smeltin Since, inthe practice of the invention, al of the contaminating metals appear tobehave similarly, we will here1n more particularly describe theinvent1on w1th respect to the elimination of lead. The nvention may bepracticed solely for the elimination of lead without special regard tothe el mination of other metals, or it may be practiced for theelimination of any one or more of the contaminating metals. In general,the elimination of substantially all of the lead bythe practice of theinvention will at the same time effect a substantial elimination of suchothers of the contaminating metals as may be present in the zincsmelting charge. In the interests ofconciseness the appended claims aredirected particularly to lead removal, but We intend thereby to cover orinclude the removal of any one or more of the aforementionedcontaminating metals.

Thepresent invention is basedon our discovery that lead can be almostcompletely removed from the gaseous product of the zinc smeltingoperation by passing the gaseous product through an eliminating ordemedium composed of at least one ingredient of the zinc smelting chargemaintained under reducin conditions at an appropriate and carefu lyregulated elevated temperature. We have further found that practicalconsiderations make it desirable to supply the gaseous product to thede-leading medium in a substantially continuous stream of relativelyconstant volume and composition and practically free of oxidizing gases.

esium, germanium and thallium, are

' at a regulated temperature sufficiently low.

Based on these discoveries, the invention involves conducting the aseousproduct resulting from the reduct on or smelting of a charge ofzinciferous material containing lead through a hot de-leadingmedium-composed of at least one in redient of the zinc reducing chargeprefera ly about to be subjected to the re ucing operation, maintainedto efiect substantial elimination of lead from the, gaseous product. Thezinc reducing operation is preferably conducted so as'to produce andsupply to the de-leading medium a substantially continuous stream oftheresulting gaseous product which should preferably be of relativelyconstant volume and composition and practically free of oxidizing gases.The de-leading medium is appropriately confined and arrangedintermediate the zinc smelting chamber and the zinc recovery apparatusso that the de-- ,leaded gaseous product passes, preferably in asubstantially continuous stream, from the de-leading medium to the zincrecovery apparatus.

While the de-leading medium may be composed of any ingredient of thereducing charge, we prefer to employ the reducing charge itselfconsisting of the mixed zincifer ous material and carbonaceous reducingagent. The de-leading medium should provide a multiplicity of tortuouspaths for the flow therethrough of the gaseous product and should yet besufficiently porous to permit the free passage of the gaseous product.These conditions are satisfactorily attained when the de-leading mediumis composed of a body of aggregates. The aggregates may be naturallyformed such as crushed or broken coke, coal or zinc ore, or may beartificiall formed as by briquetting, sintering and t e like. Theaggregates should be approximately uniform in size in order that theporosity of the de-leading medium as a whole may be substantiallyuniform. Furthermore, in order to provide the desired multiplicity oftortuous gas passages, the aggregates should not be too large. We havesecured very satisfactory results with a deleading medium composedof'briquettes approximately three inches in diameter or thicknessconfined in avertically disposed cylinder about 15 inches internaldiameter and about 6 feet long or high, where approximately one ton ofzinc metal was recovered each 24 hours from the gaseous product passingthrough the de-leading medium.

It is our belief that the removal of lead by the eliminating medium ismost effective, and probably only possible, when the lead is present inthe reduced state. The de-leading medium must therefore be maintainedunder 1 reducing conditions or in a reducing atmosphere free of anyoxidizing influence, in order to inhibit theoxidation of metallic leadand zinc, and, if necessary, to reduce any OXlCllZBd lead or zinc thatmi ht be present in the gaseous product. Shou (1 air or other-OXlCllZlIlg gas leak into or otherwise enter the enclosure for thede-leading medium, the effect veness of the lead removal is seriouslimpaired, if not completely destroye Preferably, the reducing operationis conducted so that the gaseous product thereof Y which lead compoundswill be volatilized and at which any substantial amount of lead willremain with the gaseous product, under the prevailing conditions ofoperation. Such temperature regulation is essential where the de-leadingmedium is composed in whole or in part of zinciferous material in orderto effect the desired lead elimination without substantial reduction ofthe zinciferous ma-.

terial of the de-leading medium. In practicin the invention we havesecured very satisfactory results by maintaining the deleading medium ata temperature intermediate the temperature at which zinc is reduced fromits compounds and. the temperature at which metallic zinc vapor iscondensed, and of course below the temperature at which lead will remainwith the gaseous product, under the prevailing operating conditions,whereby no substantial condensation of mm vapor takes place in thede-leading medium. a

The desired temperature regulation and control of the de-leading mediummay be effected in anyappropriate and convenient manner. This may beconveniently done by surrounding the de-leading medium with means forvarying or adjusting the heat radiation therefrom. We have securedexcellent results in practice by confining the deleading medium in avertical tube several feet in length and surrounded by heat insulatingmaterial of variable thickness or effectiveness. By appropriatelyadjusting the effectiveness of the heat insulating material, theradiation of heat from the tube can be so controlled as to maintain thedesired temperature of the de-leading medium.

We have found that the character and composition of the gaseous productresulting from the zinc reducing operation has an important bearing onthe effectiveness of the removal of the lead in accordance with theprinciples of our invention. The best results are obtained when thegaseous product is a substantiall continuous stream of zinc vapor andcar on monoxide relatively constant in volume and composition andpractically free of oxidizing gases. Such .a aseous product may beadvantageously obtalned in the process of smeltin an agglomerated orbriquetted charge of zmciferous and reducing materials in accordancewith the principles disclosed in the copending application Messrs.Breyer and Bunce, Serial No. 163,902, filed January 27,1927.

Where the process of the aforementioned Breyer and Bunce application iscarried out in an upright or vertical retort, the improve- -ments of thepresent invention may advantageously be embodied in the pro ress byprviding an upper prolongation o the retort, above the reducing zonetherein, adapted to confine the de-leading medium which in this casewill be composed of a body or column of the agglomerated zinc smeltingchar e itself about to be advanced or introduce into the reducing zoneof the retort. The agglomerated charge. as a whole then progressivelypasses through the vertical retort and its prolongation and is heated inthe reducing zone of the retort to a sufficiently high temperature toreduce compounds of zinc and volatilize the resulting metallic zinc andin the prolongation of the retort is maintained at an appropriate tema5perature to effect substantial removal of lead. The de-leading medium isthus superposed on the zinc-reducing charge undergoing reduction'and,with appropriate renewal or introduction of fresh charge at the top,progressively descends from the de-leading zone to the smelting zone,and the worked-off or exhausted agglomerates' are appropriatelywithdrawn from the bottom-of the retort.

The de-leaded gaseous product is withdrawn from the prolongation at ornear the top of the de-leading body. of agglomerates and is conducted tothe zinc recovery apparatus, such as a condenser for zinc metal.

' In the accompanying drawing, we have illustrated an apparatus adaptedfor the practice of the present invention in conjunction with theprocess of reducing zinciferous material disclosed in the aforementionedBreyer and Bunce application. It is to be understood that the drawing isillustrative, and that the invention may be practiced in other types orforms of apparatus. It is furthermore to be understood that theinvention is not limited to this particular process of reducingzinciferous material, but is generally applicable to any smeltingtreatment of zinciferous material containing lead.

The single figure of the drawing is a sectional elevation ofthe upperportion of a vertically disposedsmelting retort and auxiliaries forpracticing the improvements oi the invention. The vertical retort 5 isappropriately mounted within the heating chamber or laboratory 6 of anappropriate furnace structure 7. The retort may be heated by electricenergy, by coal, oil'or gas fuels or in any other appropriate manner.The retort 5 extends through the roof of the furnace structure 7 to adistance of several feet above the top of that structure thereby formingwhat may be termed an upper prolongation 5' of the retort. This upperprolongation may be integrally built with the retort proper or may be aseparate unit superposed on top of the retort. The integral constructionis preferred since joints and the possibility of air leakage into theretort are thereby avoided.

The prolon ation 5 of the retort is surrounded by a ayer 8 of heatinsulating material, such as dust coal, appropriately confined by asurrounding sheet metal casing 9. Near the topof the prolongation 5 agas oiftake 10 is provided communicating with a condenser 11. Thecondenser illustrated in the drawing is of the multi-channel typecomprising a gas distributing and molten metal collecting chamber 12communicating with the lower ends of a multiplicity of upright channels13. Condensers of this type are described in detail in the copendingapplication of Frank G. Breyer, Serial No.- 167,135, filed February 10,1927.

The agglomerates of mixed zinciferous material and carbonaceous reducingagent are introduced into the vertical retort through an appropriatecharging device (diagrammatically indicated by 14) at the top of theprolongation 5. This charging device is '0 such construction that no airenters the top of the retort and little or none of the gaseous productescapes, and the agglomerates are introduced into the retort withoutblocking the gas off-take 10. The retort including its upper rolongationis filled with the agglomerated charge up to about the level of the gasoff-take 10. Thespent residues or worked-off charge are withdrawn fromthe bottom of the retort 5 in a continuous manner or at appropriateperiodic intervals, thereby making room for the introduction, from timeto time, of fresh agglomerates through the charging device 14. Theretort operates in substantially a continuous manner. That portion ofthe retort within the heating chamber 6 is subjected to a sufl'icientlyhigh temperature to bring about .the reduction of the compounds of zincin the smeltin zone of the retort and the volatilization of theresulting metallic zinc. The gaseous products of the reducin operationrise in the retort 5 and pass through the relatively cooler body ofagglomerates confined in the prolongation 5. These agglomerates areabout to enter the smelting zone of the retort 5 but while functioningasthe deeading medium are superposed on' the main body of agglomeratesundergoin reduction. The temperature of the b y of agglomerates withinthe prolon ation 1s lcontrolled, by increasing or dimmi'shing thethickness of the insulating layer 8 or by other appropriate temperatureregulating zinc ore (containing from 65-70% .of zinc means, so as tomaintain the agglomerates at a temperature sufliciently low to reventvolatilization of lead compounds an to effect substantial elimination oflead without condensing any substantial amount of zinc vapor. The thusde-leaded gases pass through the off-take 10 into the condenser 11 wheresubstantially all of the zinc vapor is condensed to zinc metal.

The following specific example illustrates the principles of the presentinvention as.

practiced in an apparatus of the form shown in the accompanying drawing,although it is to be understood that this example is merely illustrativeand in no sense restrictive of the invention. 7

The charges was made up of approximately 50 parts by Weight of finelydivided and 1.5 to 3.5% of lead) and 50 parts by weight of a bituminouscoking coal. The zinc ore and coal were each crushed so thatapproximately 80% passed through a 20- f mesh screen, and were thendumped into-a dry pan Ohilian mill and subjected to the mixingand'comminuting action of the mill for some minutes From the Chilianmill, the mixed material was taken to a briquetting press and formedinto. semi-round briquettes by a compressive force of approximately 2000pounds to the square inc The briquettes, without drying, were chargedinto an externally heated vertical coking retort. In this retortthebriq'auettes Were subjected to a coking temperature of about 950 .C.for about 1 hours. The

coked briquettes were transferred without substantial loss of heat fromthe coking retort to the prolongation 5 of the vertical smelting retortand introduced therein at the rateof approximately 180 pounds atintervals of 45 minutes. he temperature within the heating chamber 6 wasabout 1100 to 1250 C., and the body of de-leadingagglomerates in theprolongation 5 was maintained at a temperature of about 800 to 900 C. In

the particular example being discussed, the retort 5 was about 25 feetlong (high) and slightly over 15 inches internal diameter, while theprolongation 5' was about 8 feet long. The retort 5 and prolongation 5were built as a unitary structure of silicon carbide circle brick,supported solel at the base and not otherwise tied into the mace.structure.

The upper level of the bri uetted charge was maintained at the level 0the condenserofi-take. 10. This was accomplished by withdrawing from thebottom of the retort 5 an appropriate amountv of worked-off bri uetteswhile charging fresh briquettes into 1: e top :of. the retort. quettesin theprolongation 5' of e retort above the top of the furnace structure7 was The column or bod or brithrough the column of de-leadingbriquettes in the prolongation 5f substantially all of the lead wasremoved from the gaseous product phere within the prolongation 5. Inpassing and remained with the de-leading briquettes.

In the-example under discussion, the lead content of the zinc metalcollected in the condenser 11 varied from 0.019 to 0.050%. Op- .eratingunder the same conditions, except that the upper level of the bri uettedcharge 7 in the retort is maintained at a out the level of the arch ofthe furnace structure 7, the lead content of the condensed 'zinc metalvaries from 0.5 to 1.25%. Likewise, working this same ore in an ordinaryzinc distillation furnace in accordance with the customary spelterretort practice, the resulting zinc metal contains 1% lead and over.Applying the principles of the invention t a zinc ore containing arelatively small amount of lead, smelted in accordance with the methodof the invention just described, we have succeeded in producing zincmetal containin from 0.0024 to 0.0032% lead.

Treating t is same ore by the same procedure,

but maintaining the charge level in the retort atabout the'level' of thefurnace arch, the resulting zinc metal contains from 0.08 to 0.12% lead.Likewise, in treating this same orein accordance with the presentspelter retort practice, the resulting zinc metal contains from 0.08 to0.12% lead.

The lead removed from the gaseous roduct of the smelting operation bythe deeadingv body of agglomerates accompanies the agglome rates intothe smelting zone of the retort in a condition or form less readilyreturned to the aseous product than the condition 'or form in which thelead occurs in the zinciferous'mate'rial. Just what happens to this leadin the smelting zone, we are not prepared to say, but it, in large partat least, passes out of the bottom of the retort with the worked-ofi'residues. Whatever the correct explanation of the phenomenon may be, thefacts themselves are clear, and almost com lete de-leading of thegaseous product is e ected in its passage through thetemperature-controlled de-leading body of agglomerates.

. It will be clear from the foregoing description that carefulregulation and control of the temperature of the body of de-leading ag'lomerates, or other form ofzinciferous and/or carbonaceous material ofthe smelting charge, is essential for the efiective'elimination of leadwithout the condensation of any substantial amount of zinc vapor. Thistemperature regulation and control is most advantageously accomplishedin the apparatus illustrated in the drawing by controlling the heatradiation from the prolongation 5'. This may be conveniently done byproviding the sheet metal casing 9 with doors, or the like,through'whieh the dust coal insulation 8 surrounding the prolongation 5'may be in-' creased or diminished. Other appropriate means oftemperature regulation and control may be used, The temperature of thegases within the prolongation 5' is determined by appropriatelypositioned pyrometers or other heat measuring instruments.

The advantages of the invention will be manifest to those skilled in theart. The lead elimination is effected by the smelting charge itself, andreferably just preceding its introduction into the reducing chamber. Bysuperposing the de-leadin body of charge on the charge undergoing reuction, all extraneous apparatus is avoided and joints or mechanicalconnections through which air might leak into the system are eliminated.Furthermore, the superposed column of de-leading agglomerates provides arelatively lon path for the de-leading operation, and a fords excellentopportunity for close temperature control. v

It is important that the de-leading body of charge be maintained in areducing atmosphere free of any oxidizing influences. To' prevent air oroxidizing gases being carried into the prolongation 5' during theintroduction of fresh charge, it is our preferred practice to introducethe charge into the prolongation 5 at a temperature at which there issuflicient gas evolution from the fresh charge to prevent the entrainingof air. Should air or other oxidizing gas leak into or otherwise enterthe de-leading body of charge, the effectiveness of the lead removalwill be seriously impaired, if not completely destroyed. This is one ofthe chief advantages resulting from our preferred unitary constructionof the retort 5 and prolongation 5', since air leakages are therebyeffectively inhibited.

While. in our preferred practice, the de- Y leading medium is composedof the mixed reducing or smelting char e, the medium may, if desired, becompose of any ingredient of the reducing charge, such as thezinciferous material alone, or the reducing agent alone. Again, while itis our preferred prac- .tice' to superpose the de -leading medium on.newal of the de-leading medium, other ways of confining the de-leadingmedium and of renewing the medium from time to time may be employed. Weconsider it advantageous to progressively move the de-leading medium Ina direction opposite to that of the direction of flow of the gaseousproduct, and to renew the medium from time .to time by fresh de-leadingmaterial added thereto at a temperature approximating the temperature atwhich the medium is maintained. Furthermore, while it is our preferredpractice to conduct the'de-leading without substantial condensation ofmetallic zinc vapor in the .de-leading medium, this is not essential,sincewhatever zinc is condensed in the de-leading medium is readilyrevolatilized and recovcase, the practice of the invention enables theproduction of zinc products more nearly leadfree than could otherwise beobtained by pyrometallurgical methods from the leadcontaining zinc ores.

We claim:

1. The improvement in the reduction of zinciferous material containinglead which comprises conducting the gaseous product'of the reducingoperation through a hot body of the reducing charge maintainedat a related temperature suiiiciently low to e ect substantial removal of leadfrom said gaseous product, and subjecting the thus .deleaded gaseousproduct to appropriate treatment for the recovery of the zinc contentthereof. ,7 c

2. The improvement in the reduction of zinciferous material containinglead which comprises conducting the gaseous product of the reducingoperation through a body of the reducing charge maintained at atemperature of from 800 to 900 C. and thereby effecting substantialremoval of lead from said gaseous product, and subjecting the thusdeleaded gaseous product to appropriate treatment for the recovery ofthe zinc content thereof.

3. The improvement in the reduction of zinciferous material containinglead which comprises conducting the gaseous product of the reducingoperation through a hot body of zinciferous material containing leadwhich comprises conducting the gaseous product of 10 the reducingoperation through a hot body of the reducing charge about to be subected to the reducing operation and maintained at aregulated temperaturesufiiciently low to effect substantial removal of lead from said gaseousproduct, progressively moving said de-leading body of the reducingcharge in a direction opposite to the direction of flow of the gaseousproduct therethrough, and subjecting the thus de-leaded gaseous productto appropriate treatment for the recovery of the zinc content thereof. 7

5. The improvement in the reduction of zinciferous material containinglead which comprises conducting the gaseous product of 2 the reducingoperation through a hot body of the reducing charge about to besubjected to the reducing operation and maintained at a regulatedtemperature sufficiently low to effect substantial removal of lead fromsaid gaseous product, renewing said de-leading body of the reducingcharge from time to time by fresh reducing charge added thereto at atemperature approximating that at which the-de-leading body of charge ismaintained, and subjecting the thus de-leaded gaseous product toappropriate treatment for the recovery of the zinc content thereof. 4

6. Theimprovement in the reduction of zinciferous material containinglead which comprises conducting the gaseous product of the reducingoperation through a hot body of the reducing charge about to besubjected to the reducing operation and maintained at a regulatedtemperature sufficiently low to effect substantial removal of lead fromsaid gaseous product, progressively moving said de-leading body of thereducing charge in a direction opposite to the direction of flow of thegaseous product therethrough, renewing said de-leading body of thereducing charge from time to time by fresh reducing charge added theretoat a temperature approximating that at which the de-leading body of'charge is maintained, and subjecting the thus de-leaded gaseous productto appropriate treatment for the recovery of the zinc content thereof. YY

7 The improvement in the reduction in an externally heated uprightretort of an agglomerated charge of carbonaceous reducing agent andzinciferous material containing lead which comprises conducting thegaseous product of the reducingoperation through a body of freshagglomerates about to be subjected to the reducing operation andmainagglomerates maintained at a regulated temtained at a temperature'sufiicientl low to effect substantial removal oflead rom said gaseousproduct without condensin an substantial amount of zinc vapor, an sujecting the thus de-leaded gaseous product toappropriate treatment forthe recovery of the zinc content thereof. v

8. The improvement in the reduction of zinciferous material containinglead-which comprises subjecting coked agglomerates of the zinciferousmaterial and a carbonaceous reducing agent to a reducing o eration,conducting the gaseous product 0 the reducin operatlon through a hotbody of the coke perature sufficiently low to effect substantial removalof lead from said gaseous product, and subjecting the thus de-leadedgaseous product to appropriate treatment for the re-' covery of the zinccontent thereof.

9. The improvement in the reduction of zinciferous material containinglead whih comprises progressively passing a charge of the zinciferousmaterial and an appropriate reducing agent through a reducing chamberheated to a sufliciently high temperature to reduce compounds of zincand volatilize the resulting metallic zinc, conducting the gaseousproduct of the reducing operation through a body of fresh charge aboutto be introduced into said reducing chamber and. maintained at aregulated temperature sufliciently low to effect substantial removal ofleadfrom said gaseous product, and subjecting the thus de-leaded gaseousproduct to appropriate treatment forrthe recovery of the zinc contentthereof.

10. The improvement in the reduction of zinciferous material containinglead which comprises progressively passing an agglomerated charge of thezinciferous material and carbonaceous reducing agent through a reducingchamber heated to a sufiiciently high temperature to reduce compounds ofzinc and volatilize the resulting metallic zinc, conducting the. gaseousproduct of the reducing operation through a body of fresh agglomeratesabout to be introduced into said reducingichamber and maintained at atemperature su ciently low to efl'ect substantial removal of lead fromsaid gaseous product without condensing any substantial amount of zincvapor, and subjecting the, thus de-leaded gaseous product to appropriatetreatment for the recovery of the zinc content thereof.

11. The improvement in the reduction of zinciferous material containinglead which comprises progressively passing a charge of Ill thezinciferous material and an appro riate reducing agent through anupright re ucing chamber in which the charge is heated to a sufficientlyhigh temperature to reduce compounds of zinc and volatilize theresulting metallic zinc, conducting the gaseous product of the reducingoperation through a hot body of fresh charge confined in a prolongationof the reducing chamber'and superposed on the charge undergoingreduction and maintained at a regulated temperature sufliciently low toeffect substantial removal of lead from said gaseous product, andsubjecting the thus de leaded gaseous product to a proprite treatgaseousproduct of the reducin operation is conducted through a hot body 0 freshcharge superposed on t e charge undergoing reduction and maintained at aregulated temperature sufliciently low to eifect substantial removal oflead from said gaseous product, introducing fresh charge into the top ofsaid retort at a temperature approximating the temperature maintained insaid superposed de-leading body of charge, and subjecting the thusde-leaded aseous product to appropriate treatment or the recovery of thezinc' content thereof.

13. The improvement in the reduction of zinciferous material containinglead which comprises progressively passing an a 10merated charge of thezinciferous materia and an appro riate reducing agent through an upri htre ucing chamber in which the charge is eated to a suficiently high temerature to reduce compounds of zinc and v0 atilize the re'sultinmetallic zinc, conducting the gaseous pro not of the reducing operationthrough a hot body of fresh agglomerates'confined m a prolongation ofthe reducing chamber and superposed on the charge undergoing reductionand maintained at a temperature suficientl low to effect substantialremoval of lead .om said gaseous product, and subjecting the thusde-leaded gaseous product to a one product without condensing anysubstantial amount of zinc vapor, and subjecting the thus de-leadedaseous product to appropriate treatment or the recovery of the zinccontent thereof.

15. The improvement in the reduction of zinciferous material containinglead which comprises progressively passing an agglomerated charge of thezinclferous material and an appropriate reducin agent through an uprightreducing cham er in which the charge isheated to a sufficiently hightemperature to reduce compounds of zinc and volatilize the resultingmetallic zinc, conducting the gaseous product of the reducing operationthrough a hot body of fresh agglomerates confined in a prolongation ofthe reducing chamber andsuperposed on the charge undergoing reductionand maintained at a temperature sufiicientlfy; low to efiect substantialremoval of lead om said gaseous product, introducing fresh agglomeratesinto said prolongation at a temperature approximating the temperaturemaintained in said superposed-de-leading body of agglomerates, andsubjecting the thus de-leaded gaseous product to appropriate treatmentfor the recovery of the zinc content thereof.

In testimony whereof we aflix our signa- EARL H. 'BUNCE. GEORGE 'T.MAHLER.

tures.

propriate treatment for the recovery of t e zinc content thereof.

14. The improvement in the reduction of zinciferous material containinglead which comprises progressively passing an ag 10merated charge of thezinciferous materia and carbonaceous reducing agent throu h a verticalretort in one rtlon of which t e charge is heated to a su ciently hightem I rature to reduce compounds of zinc and v0 atilize the resultinmetallic zinc and in another portion of whic the gaseous product of thereducin operation is conducted through a body 0 fresh charge superposedon the chargeu'mier reduction and maintained at a fl t tem raturesuflicientl low. to efiect subetanti removal of lead- 111 said gase- III

